It is the objective of this project to study the development of behavior and language in children with inborn errors of metabolism. A major focus will be on patients with galactosemia, maple syrup urine disease, and organic acidemia, but a full spectrum of children with metabolic disease will be studied. Each patient will be defined as fully from the metabolic point of view as current methodology permits. Where available, therapeutic interventions will permit studies before and after therapy. Each patient will be studied in the Neurologic Core and by magnetic resonance imaging of the brain. Behavioral studies will focus on cognitive development and the acquisition of language. Another goal of this research will be to continue to monitor infants and children entered into other studies in the Center for the presence of metabolic disease. This will be accomplished by the study of the urine with a battery of screening tests, as well as quantitative analysis of amino acids and organic acids.